Raging Sloth Tech

How to pick a digital camera


An easy to understand guide for the non/semi-technical aspiring photographer



So I’ll start off by saying that there are plenty of guides on this around the internet. What I’ve noticed however is that there tends to be a lot of guides that are absurdly simple and a lot of guides that are heavily technical. This is my attempt to bridge the gap and give you a quick and easy way to make a reasonably well informed purchasing decision when buying a digital camera.

Update


Since writing this article I've found out about DXOMark where different cameras are analyzed for their image quality (lens too if you're interested in a DSLR or similar). I heavily recommend this site for comparing potential purchases http://www.dxomark.com/index.php/Cameras/Camera-Sensor-Database

General points



So there are obviously going to be multiple things that a person is interested in when buying a camera. The most important thing to consider is, what you’re going to do with it. Where are you going to take it? Skydiving? Scuba diving? To a studio with lots of lights? Will you be going long periods of time with it and no access to power for charging? For example when I made my most recent purchase I went for the S95 over the more capable Canon G11 (or G12 which has since come out) because the S95 is pocketable and the whole point was to get a nicer pocketable camera for when I couldn’t or didn’t want to lug around my DSLR.

Only you can determine what features you absolutely need in a camera so I’ve concentrated this article on trying to judge image quality differences. I’ve made the assumption that you are looking for a point and shoot style camera and that you basically want to take a few pictures of regular life.

But I want DSLR advice!



Plain and simple, buy a Nikon or a Canon and you’ll be happy. Personally I went with a less expensive (drastically less expensive) Crop sensor Rebel XSi as the drastic price difference was more meaningful to me than the slightly better image quality. If you have the money and the will to spend it though a full sensor Canon or Nikon is what the pros use.

Common scams associated with buying a Camera



I actually had this happen to me when I bought my S95. The company I bought it from called me on the phone to confirm my order (which had already been charged to my credit card and confirmed by them...) and also to let me in on some “helpful advice”.

30 minute batteries?



The first thing the guy on the phone told me was that the S95 was a “powerful machine” and the battery only lasted 30 minutes... One of the negatives of the S90 and S95 is that the battery life isn’t all that long compared to other cameras (it is after all a very powerful machine), however, companies don’t usually make cameras with 30 minute battery lives because people wouldn’t buy them. The guy on the phone may have believed what he was saying but someone in the company was lying to try and get me to spend my hard earned cash on a basically identical battery at a crazy price (they claimed to have 3 and 5 hour batteries... That fit in the same battery slot?) So basically don’t buy into that crap. If you want an extra battery get an extra one, but read up on this sort of thing and make sure you get a compatible battery. If the battery you buy isn’t made by your camera manufacturer you damn well better pay less than what one from the manufacturer would have cost or you’ve been ripped off. I just told the guy I wasn’t going to buy a battery till I researched the issue online. I have a feeling that any camera you buy from them is a “powerful machine” with only 30 minutes of battery life...

Error Free memory cards?



The next thing up was an EF SD card, or Error Free SD card. Just about all cameras that are out nowadays take SD cards with a few exceptions (we are all looking at you Sony...) Do you know anyone who has had substantial problems with storage errors and their photos? No? That’s because the idea of an error free card is a scam. I’m not sure what they are even claiming the card does that a regular SD card doesn’t do. Plain and simple, don’t shell out for one of these things. Buy your SD cards online wherever you can find the best deal for the size of the card. SD cards have speed ratings (look at your camera specifications it may need a certain rating for things like video to work right) and capacities and versions (this is basically linked to capacity, don’t buy a card that is bigger than your camera supports or it might not work) but there is no such thing as an Error Free memory card. This is like an MP3 ready speaker or a high capacity litre jug. I felt like educating the guy on the phone, but I felt more like moving on with my day so I just said “yeah I think I have one of those.”

On to image quality



The oft told but not often heard truth about MegaPixels



I should start off by saying that every time someone asks me how many mega pixels a camera has a little part of me dies inside. When buying a tripod would you ask “how many inches does it have?” or “how high can it be set to?” The thing is that Megapixels are a measurement of resolution and besides that they are a terrible measure of camera quality. Resolution of course is how many tiny little dots go together to make up a photo. So if I have a resolution of 1x1 I have 1 pixel (1*1=1) and basically my photo is going to be a single square of colour. If I have a resolution of 2x2 I have 4 pixels (2*2=4) and I’ll have an image made up of four large squares of colour. Of course a real camera needs a significantly higher resolution than this to make a real photo, but companies would have you believe that the more pixels the better, always. The problem with this is that not all pixels are created equal.

Don’t be scared but I’m going to explain signal to noise ratio



So imagine you are in a room and trying to talk to someone on the other side. If you scream it is more likely that the other person will hear you, but if the room is empty this might not be necessary and if the room is filled with screaming people you might not get your message through no matter how loud you scream.
So how does this relate to a camera? Well, for your camera the signal is light and noise is anything that negatively affects either the light reception or your camera’s ability to measure it, perhaps an imperfection in your lens or interference in the electronics. As such your Camera sensor’s ability to sort out any potential noise and accurately measure the light that enters its lens is very important for getting a nice detailed photo. Here is where the big companies’ Megapixels fail you. The thing is that most cameras of the same approximate size and function have sensors that are physically about the same size. So if I have a 1x1 sensor and a 2x2 sensor each the same physical size, the pixel elements in the 2x2 sensor each get 1/4 the amount of light that the 1x1 sensor gets. So every time you add a megapixel you reduce the signal in the signal to noise ratio and would have to do something else to the camera to get the same quality per pixel as a camera with a lower resolution.
Now if there is just a tonne of light out there on a really bright day there will be lots of signal to go around so the difference will be negligible to non-existent. In low light conditions this is going to make a big difference though. When I moved from an older Sony 5MP camera, the model of which I can’t remember, to my Samsung L210 (10MP) I noticed very quickly that while in high light environments it was much more detailed, in low and medium light environments the photos looked about the same, but zooming in on the Samsung pictures there was a lot of noise (strange shades of green and red that shouldn’t have been there), so I was getting basically the same photo but twice the file size....

So if Megapixels are a marketing scam, how do I compare image quality?



The best answer to this question is to google around and look at photos taken by various cameras. Every now and then a site will have a showdown between various brands and often post a number of comparison shots. If you can’t find comparisons you want and are looking for a nice rule of thumb way to compare cameras I stumbled the other day across a site that actually gives
sensor density comparisons. If you follow that link and then click on the brand of camera your interested in it will show you not only the resolution (measured in Megapixels... please say resolution instead...) but also the pixel density (the number of pixels per square centimetre, lower is better). If you take a look at the Canons you’ll notice that the lower end consumer devices can tend to go Megapixel crazy with numbers like 12 and 14MP giving them pixel densities as high as 50MP/square centimetre. While on the higher end compact cameras they seem to all be 10MP and have pixel densities like 23MP/square centimetre, like my awesome S95. If you look at the DSLRs you’ll see numbers like 3.1MP/square centimetre for the Canon 1D Mark IV (the highest end 35mm format Canon DSLR, which amazon has listed for just under 5k with no lens...). In fact my S95 even has a low light feature that allows you to use 4 pixel sensors as one to get a lower res image with higher low light quality. You can see some quick comparison shots I’ve taken below:

Quick Comparison photos


Please note that I’ve been relatively happy with my Samsung L210 it is simply a lower tier camera not meant to compete with the high end S95 that I now own, it is also a couple of years old now while at the time of typing the S95 is brand new. I’m simply using the cameras I have available to me.

Samsung L210 10.2MP 36MP/square centimetre


Samsung L210 36MP/square centimetre sensor shot in low light
Notice how the photo as taken is relatively dark. What you might not realize is that this was a full 1 second exposure... The shot also has less detail than the S95 shot.

S95 10MP 23MP/square centimetre


low light photo taken with Canon S95 23MP/square centimetre
This shot was taken in identical lighting conditions. You can plainly see that the shot is more detailed what isn’t apparent to the eye immediately is that this was taken with a quick 1/13th of a second exposure (part of the detail loss is probably due to movement during the much longer 1s exposure the Samsung does have dual image stabilization though and the denser sensor made the 1s exposure necessary). EDIT (The lens would also be a factor here and the sensor qualities but I'm trying to make a point alright :) )


I would again like to mention though that sensor density isn’t the only thing that affects image quality. There is also an element of sensor quality that isn’t easy to express in numbers and certainly not least important is the lens. This is why the best way to judge image quality is to look at images taken with various cameras and do a comparison or read reviews done by experts. Again as a rule of thumb however those cameras with lower sensor densities are usually made with image quality in mind and one can reasonably expect them to be paired with a quality lens.

Final Thoughts



To sum up, you need to consider more than just image quality. It won’t do you much good to buy an S95 and take it in the water without the optional waterproof casing now will it? and perhaps you would have been better off getting the canon model that comes already waterproofed to save the hassle of the separate case. So the basic plan is
  1. Decide what you want to do with your camera;
  2. make a list of cameras that do those things
  3. look at photos taken with those cameras on the internet (try to get full resolution and zoom way in);
  4. If you aren’t really sure or can’t find good comparison photos take a look at the sensor density. EDIT check out DXO Mark which will give you a better technical analysis of the camera if it is in their database
I also heavily recommend getting a nice camera (read high end/expensive) and taking good care of it. There are enough 3rd party manufacturers now that you don’t have to worry about being stuck with a nice camera and a worn out battery that costs as much as the camera to replace (why I replaced my sony with the samsung) So think about getting a camera that you’ll keep for years to come and spend enough that you’ll be happy with all the photos you take with it (I missed out on a really great photo in Europe because it was dark out and all I had was my L210 which as shown isn’t great in even moderately low light and is limited to a max 1s exposure length, I took the photo and it looks like crap...)

and finally, take care of one another :) If you know someone who is looking to buy a camera, send them to this or another website that exposes these details and if you’re in a store and you see some people looking at cameras talking about Megapixels (or being told about them by a store clerk) interject and explain why they’re going down the wrong road. I’ve done this at Costco a few times and people are really grateful for the advice, especially parents who want a nice camera and don’t have a lot of expendable income or time to really research the subject. On a completely unrelated note, I also stop people from buying cables at Best Buy and refer them to
Monoprice, but that’s kind of a different story...